The present invention relates generally to an optical disk cartridge assembly and, more particularly to an optical disk cartridge assembly provided with a low wear casing.
An optical disk is a data storage medium which is readable by a laser-based reading device. Optical disks known as "compact disks" or "CDs" have become increasing popular during the past few years for recording music and audio-video works. Due to the huge storage capacity of optical disks as compared to conventional magnetic storage media, optical disks known as "ROM disks" have become popular for storing computer readable information. However, until very recently, optical disks were of somewhat limited use in the computer industry due to the fact that optical disks could not be "erased" and "written" with new information, i.e. ROM disks are "read only" memory devices. However, recent technology has produced optical disks which are both computer readable and computer writable. Thus, in the future, optical disks are expected to become increasingly more important in the computer industry and may eventually replace magnetically readable and writable storage media such as "floppy disks" and "hard disks." Another recent development, the ability to provide data storage on both surfaces of an optical disk, has effectively doubled the optical disk storage capacity.
Optical disks of the type used in computer applications are generally provided in a cartridge assembly including an optical disk, a parallelepiped-shaped casing in which the disk is rotatably mounted, and a sliding reader door which selectively covers or uncovers an opening in the casing to shield or expose the disk. An optical disk reading/writing device or "optical drive" generally receives a cartridge assembly through a narrow slot provided on the front face of the device. Typically, the cartridge being inserted initially abuttingly engages a biased door in the device and is urged against the door to open it. The cartridge casing then slides over a supporting surface within the reading/writing device as it is pushed into the device. After the cartridge has been loaded into the device, a locating pin within the device is inserted through a transversely extending hole on the cartridge casing to hold the cartridge in a fixed position within the device. Prior to reading/writing, a mechanism within the device slides open the cartridge door to expose the disk to a laser.
Currently, most optical disks are hand-inserted into drives. However, for large databases consisting of many optical disks, it is preferable, and perhaps essential, to provide an optical disk storage system for storing the disks at known locations, and an optical disk handling system which is capable of retrieving a desired disk from a storage location and inserting the disk into an optical disk drive.
U.S. patent application Ser. No. 314,012 filed Feb. 22, 1989, of Wanger et al. for CARTRIDGE HANDLING SYSTEM, now U.S. Pat. No. 5,010,536, is hereby specifically incorporated by reference for all that it discloses. This patent discloses a disk storage and retrieval system or "autochanger" wherein the stored disks and an associated disk reader are arranged in a longitudinally extending, two-dimensional array consisting of vertically extending columns and laterally extending rows. This autochanger system is adapted to engage a disk, move it vertically, laterally, and/or longitudinally and then release it in order to remove it from storage, move it into aligned relationship with the disk reader, and insert it into the disk reader. The disk handling system is also adapted to flip the disk to reverse the side thereof which will be positioned in readable relationship with a reader. The system is further adapted to reorient a disk at the time it is initially inserted into the system by an operator.
Cartridge casings are subject to wear as a result of surface contact made with other objects Wear rate is generally defined as the volumetric loss of material over a unit time. A "wear factor" may be defined in terms of parameters which affect wear rate. "Wear factor", as used herein, is defined as follows:
K (wear factor)=W/FVT, where: PA1 W=volume wear (in.sup.3) PA1 F=force (lb) PA1 V=velocity (ft/min) PA1 T=elapsed time (hr)
The wear factors for various materials as specified herein are based upon wear factor measurements made in accordance with a procedure described at p. 25 of a brochure entitled: LUBRICOMP INTERNALLY LUBRICATED REINFORCED THERMOPLASTICS AND FLUOROPOLYMER COMPOSITES Bulletin 254,688, which is available from LNP (a business unit of ICI Americas, Inc.), 1831 E. Carnegie, Santa Ana, Calif., 92705, which is hereby specifically incorporated by reference for all that it discloses and which is set forth in Appendix A which forms a part of the disclosure of this application.
Currently, most optical disk casings are constructed from a thermoplastic material such as polycarbonate which has a wear factor "K" on the order of 2500.times.10.sup.-10 in.sup.3 -min/ft-lb-hr. It is applicants' discovery that such currently used casing material creates a problem in optical disk cartridge assemblies which are used in autochangers such as described in U.S. patent application Ser. No. 314,012 and such as are currently sold under the product designation C1710 by Hewlett-Packard Company having a business address of 3000 Hanover Street, Palo Alto, Calif., 94304. Applicants have discovered that in such autochangers abrasive wear of cartridge casings causes a build up of fine particles in the autochanger optical drives which contaminates the surface of optical disks, thus effecting the reading or writing operation being performed, and which also may cause jamming of the cartridge door and jamming of other malfunctions of the optical drives or various other mechanical assemblies of the autochanger. Applicants have discovered that this particle build up is produced by frictional engagement of the cartridge with various surfaces of cartridge storage cells, the optical drive(s), and the cartridge handling mechanism of the autochanger, as well as by the sliding movement of the reader doors of cartridges. These problems associated with abrasive wear of cartridges used in autochangers were to applicants' knowledge not know in the art prior to applicants' discovery.